Indexing mechanisms

ABSTRACT

An indexing mechanism wherein an index wheel having a number of spaced projections around a periphery thereof is indexed by means of an indexing mechanism which is moved to and fro to engage in turn the said projections and wherein there is a leaf spring which acts on the projections to urge same forward to the desired index position or rearwards to the desired index position.

United States Patent Bud 1 51 June 20, 1972 s41 INDEXING MECHANISMS 962,133 6/1910 Doane ..74/577 s1= 1,818,690 8/1931 Carlson ....74/S77 SF [721 Hm England 1,979,028 10/1934 Ewart ....74/577 M [73] Assignee: English Numbering Machines Limited, 2,868,026 l/ I959 Finehout et al. .....74/578 X London, England 3,136,167 6/1964 Momer ..74/i28 X Filed: 00 22, 1970 Primary Examiner-William F. ODea Assistant Examiner-F. D. Shoemaker [21] Appl' 82906 Attomey-Griffin, Branigan & Kindness [30] Foreign Application Priority Data 7 Nov. 7, 1969 Great Britain ..54,570/69 [57] ABSTRACT An indexing mechanism wherein an index wheel having a [52] US. Cl. ..74/815, 74/577 M number of spaced projections around a peri hery thefeofis i [51] Int. Cl- 053 5/12 dexed by means of an indexing mechanism which is moved to [58] Field of Search ..l74/8l5,8l3, 128,568,568 M, and fro to engage in'tum the said projections and wherein 174/568 T, 577 S, 577 SF, 577 M, 578 there is a leaf spring which acts on the projections to urge same forward to the desired index position or rearwards to the [56] References Cited desired index position.

UNITED STATES PATENTS 4 Ciainn, 8 Drawing Figures 321,062 6/1885 Tideman ..74/577 SF INDEXING MECHANISMS This invention relates to an indexing mechanism.

An object of the present invention is to provide an indexing mechanism in which an index wheel when at rest may assume only one of a number of predetermined index positions and is prevented from assuming any intermediate position.

According to one aspect of the invention, there is provided an indexing mechanism comprising an index wheel having a plurality of index positions, a plurality of projections corresponding in number to said index positions, said projections being spaced equally apart around a peripheral region of the wheel, a stepping pawl device mounted for back and forth movement and positioned to engage in turn the said projections to index the wheel in a forwards direction, and a leaf spring means lying tangentially to the wheel and positioned to press resiliently on said peripheral region and to act on said projections as the wheel is indexed and urge the wheel to each index position in the forwards direction as it is being indexed by the stepping pawl device, and in the event of the wheel being over indexed past an index position, to urge the wheel back to said index position.

According to another aspect of the invention, there is provided an indexing mechanism comprising a plurality of index wheels each having a plurality of index positions and each having a plurality of projections corresponding in number to the index positions spaced equally apart around a peripheral region of the wheel, a stepping pawl device for each wheel mounted for back and forth movement and positioned to engage in turn the said projections to index the wheel in a forwards direction, and a leaf spring means for each wheel which lies tangentially to the wheel and is positioned to press resiliently on said peripheral region and to act on said projections as the wheel is indexed and urge the wheel to each index position in the forwards direction as it is being indexed by the associated stepping pawl device, and, in the event of the wheel being over indexed past the indexed position, to urge the wheel back to said index position.

A preferred embodiment of the invention consists in a counter mechanism comprising an indexing mechanism as hereinbefore defined.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. I shows an elevation view of the mechanism, a

counter, taken on the line II of FIG. 2;

its respective drive portion 3. Since each number portion is numbered 0 to 9, the counter. wheels signify (from the right in FIG. 1) units, tens, hundreds, thousands and tens of thousands, from which it follows that, for example, the tens" wheel is required to rotate one step for each revolution of the units wheel. For this reason, each limb 11 (from the right of FIG. 1) is progressively shorter. From FIG. 2 it can be seen, that when the longest of the limbs 1 1 lies on the circumference of its respective drive wheel portion 3, the remaining four shorter limbs remain clear of their respective drive wheel portions. As the U-shaped member 8 is rotated about the shaft 4 through 36, the limb 11 which is bearing on its respective drive wheel portion engages one of the projections 5 causing that drive wheel to be rotated through 36", resulting in the corresponding number portion rotating through 36 to indicate an increase of one unit on a unit scale (not shown). When the "units" counter wheel has been driven through one revolution, the associated limb 11 drops into the slot 6 causing the limb ll of the tens number wheel to bear on the drive wheel portion of its respective number wheel. On the next rotation of the U- shaped member 8 through 36 both the tens and the units" number wheels are rotated through a step which corresponds to rotation through 36. The larger units limb 1 1 once again bears on the circumference of its respective drive wheel'portion 3, whilst the "tens" limb 11 is again rendered inoperative until the units number wheel has completed a further revolution. The sequence is followed so that on completion of one revolution of the units" number wheel the tens number-wheel rotates through one step and on completion of one revolution of the tens wheel the hundreds number wheel is rotated through one step, and so on.

The actuator mechanism 7 when actuated, for example manually, is pushed by means of the extending portion of the rod 9 so that the U-shaped member-8 rotates (anti-clockwise in FIG..2) through 36. As the U-shaped member is rotated, the engagement member 10 is biased anticlockwise about the rod-like member 9 urged by. the spring 12. The effect is to urge the limb 11 against one of the projections 5 causing the corresponding drive portion 3 to be rotated. The actuator mechanism is biased (by means not shown) to return to its initial position. This results in the return of the U-shaped member 8. The limb 11 hearing on the circumference of the drive wheel portion also returns so that the drive wheel portion has to be biased in its new position.

A pair of resilient members or spring plates 20, 21 (as shown in FIG. 3) are provided to bias the position of the number wheels 1. Each of the plates 20, 21 are-provided with spring fingers each of whichare arranged to rest on the circumference of a respective one of said drive wheel portions. As can be seen from FIG. 2 the two spring plates are arranged v tangentially to the drive portions of the counter wheels. The

7 act as stops for, the projections 5, whereas the longer fingers that (from left to right in FIG. 1) consecutive number portions back and forth about the shaft 4 through a fixed arcuate path,

corresponding to the angular pitch of the digits, in this case 36. The actuator mechanism 7 comprises a U-shaped member 8 carrying a rod-like member 9 (FIG. 2) passing through the arms thereof and extending through an arcuate slot in a side wall of a casing. Each arm of the member 8 is journalled near its free end for mounting on the shaft 4. An engagement member 10, which is journalled to be carried by the rod-like member 9, is provided with limbs 11 each positioned to engage a respective one of the drive portions 3 of the number wheels 1. By means of a spring. 12, the engagement member 10 biased so that at least one of the limbs 11 bears on 23 lie on the fingers 22 and rest against the outer surface of the'projections 5. Thus, referring to FIG. 2, whenone of the limbs 11 urges its respective drive portion 3 anticlockwise by engagement with a projection 5a the counter'wheel rotates until a projection 5d passes the end of a spring finger 22. The projection 5d isbiased in its new position by the spring finger 22 acting on the projection 50 which causes the projection 51; to be pushed past the limb 11. As the projection 5b passed the limb 11, the limb 11 is urged away from the circumference of the respectivedrivewheel against the bias of the spring 12. Once the projection 5b is passed, the limb 11 returns to contact the surface of the drive wheel portion between the projections 5a and 5b, and as the U-shaped member returns to its rest position the limb .11 returns also so that its point of con-v tact with the drive wheel portion is between the projections 5b and 5c.

In order to more fully describe the action of the spring plates 20, 21, FIGS. 4 to 8 show positions which a counter wheel may occupy during steps between index positions.

In FIG. 2 the counter wheel 1 is at an indexposition with the counter mechanism 7 at its rest position. In this index position, the spring finger 22 is lying longitudinally in contact with the drive portion 3 between the projections c and 5d so that the projection 5c abuts the free end of the spring finger 22. At this position, the spring finger 23 overlying the spring finger 22 rests on the extremity of the projection So with its line of action passing through the center of the counter wheel. The limb l l engages the periphery of drive wheel portion 3 between the projections 50 and 5b.

To rotate the counter wheel through one step to its next index position, the actuator mechanism 7 is urged forward in the direction of the arrow A (as shown in FIG. 4). This causes the U-shaped member 8 to rotate'about the shaft 4, arrow B, and as it does so the limb 11 engages -the projection 5a. Thus, referring to FIG. 4, it can be seen that the projection 5a is displaced in the forward direction of its counter wheel (i.e., anticlockwise in the drawing), by a distance related to the displacement of the actuator mechanism. In this case, the displacement of the actuator mechanism is not great enough to displace the counter wheel into its next index position by means of the limb ll acting alone. However, the projection 5d is urged into contact with the spring finger 22 until the spring finger 22 leaves the drive portion 3 so that the spring finger 22 acts on the projection 5d causing the counter wheel to be urged further in the anticlockwise direction. The counter wheel .1 continues in the anticlockwise direction until it reaches the index position shown in FIG. 5. As can be seen, the projection 5d acted on by the spring finger 23 abuts the end of the spring finger 22 so that when the actuator mechanism 7 returns to its rest position (shown in FIG. 2) the limb 11 moves clockwise over the projection 5b (FIG. 8) and rests in contact with the periphery of the drive portion 3 between the projections 5c and 5b. The spring 12 allows the engagement member 10 carrying the limb 11 to be urged away from the drive portion periphery as it passes over the projection 5b. The shape of the projection facilitates their engagement by the limb 11 when it is moved in the anticlockwise direction and disengagement when the limb moves in the clockwise direction.

Referring to FIG. 7, it can be seen that the actuator mechanism 7 is forward of its rest position beyond the next index position, causing the projection 50 to be displaced so far forward that the projection 50' is past the free end of the spring finger 22. In this case, the projection Se is urged clockwise by contact with the spring finger 22 and the outer surface of projection 5d, acted on by the spring finger 23, abuts the free end of the spring finger 22, which maintains the counter wheel in its newly occupied index position (shown in FIG. 6) as the actuator mechanism returns to its rest position.

The line of action of the spring finger 23 on a projection 5 determines whether a force obtains to rotate the counter wheel clockwise or anticlockwise. In an index position the pressure of the spring finger 23 acts normally on the adjacent projection so that the line of action passes through the center of the wheel C. In FIG. 4, it can be seen, that the line of action of the spring fingers 22, 23 on the projection 5d is such as to cause an anticlockwise movement of the counter wheel. Conversely, in FIG. 7, it can be seen, that the line of action of the spring fingers 22, 23 ensures a clockwise rotation of the wheel. The spring finger 22 therefore acts as a ratchet to step the counter wheel.

I claim:

1. An indexing mechanism comprising an index wheel having a plurality of index positions, a plurality of projections corresponding in number to said index positions, said projections being spaced equally apart around a peripheral region of the wheel, a stepping pawl device mounted for back and forth movement and positioned to engage in turn the said projections to index the wheel in a forwards direction, and a leaf spring means lying tangentially to the wheel and positioned to press resiliently on said peripheral region and to act on said projections as the wheel is indexed and urge the wheel to each index position in the forwards direction as it is bein indexed by the stepping pawl device, and in the event of e wheel being over indexed past an index position, to urge the wheel back to said index position.

2. An indexing mechanism according to claim I, wherein said leaf spring means comprises an inner leaf spring and an outer leaf spring lying on top of the inner leaf spring, each of said inner and outer leaf springs being fixed at one end and having a free end, the inner leaf spring being-located so that its free end engages the rear of a projection in each of said index positions preventing the wheel from being rotated rearwards past any index position.

3. An indexing mechanism according to claim 2, wherein the free end of the upper leaf spring engages the top of the projection the rear of which is engaged by the inner leaf spring.

4. An indexing mechanism comprising a plurality of index wheels each having a plurality of index positions and each having a plurality of projections corresponding in number to the index positions spaced equally apart around a peripheral region of the wheel, a stepping pawl device for each wheel mounted for back and forth movement and positioned to engage in turn the said projections to index the wheel in a forwards direction, and a leaf spring means for each wheel which lies tangentially to the wheel and is positioned press resiliently on said peripheral region and to act on said projections as the wheel is indexed and urge the wheel to each index position in the forwards direction as it is being indexed by the associated stepping pawl device, and, in the event of the wheel being over indexed past the indexed position, to urge the wheel back to said index position.

i a a a a a 

1. An indexing mechanism comprising an index wheel having a plurality of index positions, a plurality of projections corresponding in number to said index positions, said projections being spaced equally apart around a peripheral region of the wheel, a stepping pawl device mounted for back and forth movement and positioned to engage in turn the said projections to index the wheel in a forwards direction, and a leaf spring means lying tangentially to the wheel and positioned to press resiliently on said peripheral region and to act on said projections as the wheel is indexed and urge the wheel to each index position in the forwards direction as it is being indexed by the stepping pawl device, and in the event of the wheel being over indexed past an index position, to urge the wheel back to said index position.
 2. An indexing mechanism according to claim 1, wherein said leaf spring means comprises an inner leaf spring and an outer leaf spring lying on top of the inner leaf spring, each of said inner and outer leaf springs being fixed at one end and having a free end, the inner leaf spring being located so that its free end engages the rear of a projection in each of said index positions preventing the wheel from being rotated rearwards past any index position.
 3. An indexing mechanism according to claim 2, wherein the free end of the upper leaf spring engages the top of the projection the rear of which is engaged by the inner leaf spring.
 4. An indexing mechanism comprising a plurality of index wheels each having a plurality of index positions and each having a plurality of projections corresponding in number to the index positions spaced equally apart around a peripheral region of the wheel, a stepping pawl device for each wheel mounted for back and forth movement and positioned to engage in turn the said projections to index the wheel in a forwards direction, and a leaf spring means for each wheel which lies tangentially to the wheel and is positioned press resiliently on said peripheral region and to act on said projections as the wheel is indexed and urge the wheel to each index position in the forwards direction as it is being indexed by the associated stepping pawl device, and, in the event of the wheel being over indexed past the indexed position, to urge the wheel back to said index position. 